17 The Nervous System: Autonomic Nervous System PowerPoint Lecture Presentations prepared by Steven Bassett Southeast Community College Lincoln, Nebraska
Introduction The autonomic nervous system functions outside of our conscious awareness The autonomic nervous system makes routine adjustments in our body s systems The autonomic nervous system: Regulates body temperature Coordinates cardiovascular, respiratory, digestive, excretory, and reproductive functions
A Comparison of the Somatic and Autonomic Nervous Systems Autonomic nervous system Axons innervate the visceral organs Has afferent and efferent neurons Afferent pathways originate in the visceral receptors Somatic nervous system Axons innervate the skeletal muscles Has afferent and efferent neurons Afferent pathways originate in the skeletal muscles ANIMATION The Organization of the Somatic and Autonomic Nervous Systems
Subdivisions of the ANS The autonomic nervous system consists of two major subdivisions Sympathetic division Also called the thoracolumbar division Known as the fight or flight system Parasympathetic division Also called the craniosacral division Known as the rest and repose system
Figure 17.1b Components and Anatomic Subdivisions of the ANS (Part 1 of 2) AUTONOMIC NERVOUS SYSTEM THORACOLUMBAR DIVISION (sympathetic division of ANS) CRANIOSACRAL DIVISION (parasympathetic division of ANS) Cranial nerves (N III, N VII, N IX, and N X) T 1 T 2 T 3 T 4 T 5 Thoracic nerves T 6 T 7 T 8 Anatomical subdivisions. At the thoracic and lumbar levels, the visceral efferent fibers that emerge form the sympathetic division, detailed in Figure 17.4. At the cranial and sacral levels, the visceral efferent fibers from the CNS form the parasympathetic division, detailed in Figure 17.8.
Figure 17.1b Components and Anatomic Subdivisions of the ANS (Part 2 of 2) T 9 Thoracic nerves T 10 T 11 T 12 Lumbar nerves (L 1, L 2 only) L 1 L 2 L 3 L 4 L 5 S 1 S 2 S 3 S 4 Sacral nerves (S 2, S 3, S 4 only) S 5 Anatomical subdivisions. At the thoracic and lumbar levels, the visceral efferent fibers that emerge form the sympathetic division, detailed in Figure 17.4. At the cranial and sacral levels, the visceral efferent fibers from the CNS form the parasympathetic division, detailed in Figure 17.8.
Subdivisions of the ANS Sympathetic division Thoracic and upper lumbar nerves synapse in ganglia near the spinal cord Sympathetic activation results in: Increased metabolism and alertness Parasympathetic division Synapses are located near the target organ Parasympathetic activation results in: Energy conservation
Subdivisions of the ANS Sympathetic division All preganglionic fibers release acetylcholine. The effects are stimulatory. Most postganglionic fibers release norepinephrine.the effects are stimulatory. Parasympathetic division All preganglionic fibers release acetylcholine. The effects are stimulatory. Postganglionic fibers release acetylcholine but the effects can be inhibitory.
Figure 17.1a Components and Anatomic Subdivisions of the ANS AUTONOMIC NERVOUS SYSTEM Consists of 2 divisions SYMPATHETIC (thoracolumbar) DIVISION PARASYMPATHETIC (craniosacral) DIVISION Preganglionic neurons in lateral gray horns of spinal segments T 1 L 2 Preganglionic neurons in brain stem and in lateral portion of anterior gray horns of S 2 S 4 Send preganglionic fibers to Ganglia near spinal cord Preganglionic fibers release ACh (excitatory), stimulating ganglionic neurons Ganglia in or near target organs Preganglionic fibers release ACh (excitatory), stimulating ganglionic neurons Which send postganglionic fibers to Target organs Most postganglionic fibers release NE at neuroeffector junctions Target organs All postganglionic fibers release ACh at neuroeffector junctions Fight or flight response Rest and repose response Functional components of the ANS
The Sympathetic Division Sympathetic division consists of: Preganglionic neurons between T 1 and L 2 Two types of ganglionic neurons near the vertebral columns: sympathetic chain ganglia (lateral to the vertebral column) and collateral ganglia (anterior to the vertebral column) Specialized neurons in the interior of the suprarenal gland
The Sympathetic Division Sympathetic division Preganglionic neurons Cell bodies are in the lateral gray horns Axons enter the ventral roots Sympathetic chain ganglia (paravertebral ganglia) Control effectors in the body wall, head, neck, limbs, and thoracic cavity
The Sympathetic Division Sympathetic division Collateral ganglia (prevertebral ganglia) Neurons innervate effectors in the abdominopelvic cavity Specialized neurons Modified sympathetic ganglion in the suprarenal gland Neurons release neurotransmitters that act like hormones
Figure 17.2 Organization of the Sympathetic Division of the ANS Sympathetic Division of ANS Innervation by postganglionic fibers Ganglionic Neurons Target Organs KEY Preganglionic Neurons Lateral gray horns of spinal segments T 1 L 2 Preganglionic fibers Postganglionic fibers Hormones released into circulation Sympathetic chain ganglia (paired) Collateral ganglia (unpaired) Suprarenal medullae (paired) Through release of hormones into the circulation Visceral effectors in thoracic cavity, head, body wall, and limbs Visceral effectors in abdominopelvic cavity Organs and systems throughout body
The Sympathetic Division Sympathetic Chain Ganglia The ventral root joins a dorsal root Forms a spinal nerve Passes through an intervertebral foramen White ramus branches off the spinal nerve Goes to a nearby sympathetic chain ganglion
The Sympathetic Division Functions of Sympathetic Chain Ganglia Reduction of circulation to the skin More circulation to skeletal muscles Stimulates more energy production by skeletal muscles Releases stored adipose Stimulation of arrector pili muscles Dilation of pupils Increased heart rate Dilation of respiratory tubes
Figure 17.3a Sympathetic Pathways and Their General Functions Autonomic ganglion of left sympathetic chain Sympathetic nerve (postganglionic fibers) Innervates visceral organs in thoracic cavity via sympathetic nerves Spinal nerve Preganglionic neuron Sympathetic Chain Ganglia Autonomic ganglion of right sympathetic chain Gray ramus Innervates visceral effectors via spinal nerves White ramus Ganglionic neuron KEY Preganglionic neurons Ganglionic neurons Major effects produced by sympathetic postganglionic fibers in spinal nerves: Constriction of cutaneous blood vessels, reduction in circulation to the skin and to most other organs in the body wall Acceleration of blood flow to skeletal muscles and brain Stimulation of energy production and use by skeletal muscle tissue Release of stored lipids from subcutaneous adipose tissue Stimulation of secretion by sweat glands Stimulation of arrector pili Dilation of the pupils and focusing for distant objects Major effects produced by postganglionic fibers entering the thoracic cavity in sympathetic nerves: Acceleration of heart rate and increasing the strength of cardiac contractions Dilation of respiratory passageways
The Sympathetic Division Anatomy of the Sympathetic Chain Ganglia Each spinal nerve consists of: Preganglionic and postganglionic fibers There are: cervical sympathetic chain ganglia thoracic sympathetic chain ganglia lumbar sympathetic chain ganglia sacral sympathetic chain ganglia coccygeal sympathetic chain ganglia
Figure 17.4 Anatomical Distribution of Sympathetic Postganglionic Fibers Eye PONS Salivary glands Superior Sympathetic nerves Cervical sympathetic ganglia Middle Inferior Gray rami to spinal nerves T 1 T 1 T 2 T 2 T 3 T 3 Greater splanchnic nerve Cardiac and pulmonary plexuses Heart Lung T 4 T 4 Celiac ganglion T 5 T 5 T 6 T 6 T 7 T 7 Superior mesenteric ganglion Liver and gallbladder T 8 T 8 Stomach T 9 T 9 T 10 T 10 T 11 T 11 Lesser splanchnic nerve Spleen Pancreas Postganglionic fibers to spinal nerves (innervating skin, blood vessels, sweat glands, arrector pili muscles, adipose tissue) T 12 T 12 L 1 L 1 L 2 L 2 L 3 L 3 L 4 L 4 Lumbar splanchnic nerves Inferior mesenteric ganglion Large intestine Small intestine Sympathetic chain ganglia L 5 L 5 S 1 S 1 S 2 S 2 S 3 S 3 S 4 S 4 S 5 S 5 Sacral splanchnic nerves Suprarenal medulla Kidney Spinal cord KEY Preganglionic neurons Ganglionic neurons Coccygeal ganglia (Co 1 ) fused together (ganglion impar) Uterus Ovary Penis Scrotum Urinary bladder
The Sympathetic Division Collateral Ganglia Preganglionic neurons originate in the inferior thoracic and superior lumbar areas of the spinal cord Fibers pass through the sympathetic chain ganglia without synapsing Converge to form the greater, lesser, and lumbar splanchnic nerves Splanchnic nerves converge on the collateral ganglia
The Sympathetic Division Functions of the Collateral Ganglia Reduction of flow of blood to the visceral organs Decrease in activity of the digestive organs Stimulation of the release of glucose from glycogen in the liver Stimulates adipose cells to release energy reserves Relaxation of smooth muscles in the urinary bladder Cause ejaculation in males
Figure 17.3b Sympathetic Pathways and Their General Functions Collateral Ganglia Major effects produced by preganglionic fibers innervating the collateral ganglia: Splanchnic nerve (preganglionic fibers) Postganglionic fibers Collateral ganglion Lateral gray horn White ramus Innervates visceral organs in abdominopelvic cavity Constriction of small arteries and reduction in the flow of blood to visceral organs Decrease in the activity of digestive glands and organs Stimulation of the release of glucose from glycogen reserves in the liver Stimulation of the release of lipids from adipose tissue Relaxation of the smooth muscle in the wall of the urinary bladder Reduction of the rate of urine formation at the kidneys Control of some aspects of sexual function, such as ejaculation in males
The Sympathetic Division Anatomy of the Collateral Ganglia Splanchnic nerves innervate: Celiac ganglion: fibers innervate the stomach, duodenum, liver, gallbladder, pancreas, spleen, and kidney Superior mesenteric ganglion: fibers innervate the small intestine and the first parts of the large intestine Inferior mesenteric ganglion: fibers innervate the kidney, urinary bladder, sex organs, and terminal ends of the large intestine
The Sympathetic Division Suprarenal Medullae Fibers pass through sympathetic chain and the celiac ganglion without synapsing Proceed to the suprarenal medulla Fibers then synapse on modified neurons that when stimulated will release neurotransmitters that act as hormones: Epinephrine and norepinephrine
The Sympathetic Division Functions of the suprarenal medullae Increase alertness by activating the reticular activating system Increase cardiovascular and respiratory activity Increase muscle tone Increase the mobilization of energy reserves Increased release of lipids from adipose cells Increased breakdown of glycogen in liver cells
Figure 17.3c Sympathetic Pathways and Their General Functions The Suprarenal Medullae Major effect produced by preganglionic fibers innervating the suprarenal medullae: Release of epinephrine and norepinephrine into the general circulation Preganglionic fibers Endocrine cells (specialized ganglionic neurons) Suprarenal medullae Secretes neurotransmitters into general circulation
Figure 17.5a Suprarenal Medulla Cortex Suprarenal gland Medulla Right kidney Relationship of a suprarenal gland to a kidney
Figure 17.5ab Suprarenal Medulla Cortex Modified neurons (sympathetic ganglion cells) of suprarenal medulla Capillaries Medulla Nucleolus in nucleus Suprarenal medulla LM 426 Relationship of a suprarenal gland to a kidney Histology of the suprarenal medulla, a modified sympathetic ganglion
The Sympathetic Division Sympathetic activation and neurotransmitter release Sympathetic ganglion fibers release acetylcholine at the synapse with ganglionic neurons These are cholinergic synapses The stimulation of ganglionic neurons causes the release of norepinephrine at the neuroeffector junction These terminals are adrenergic Some ganglionic neurons also release acetylcholine Especially at the neuroeffector junctions of skeletal muscles
Figure 17.6 Sympathetic Postganglionic Nerve Endings Preganglionic fiber Ganglionic (myelinated) neuron Ganglion Postganglionic fiber (unmyelinated) Varicosities Vesicles containing norepinephrine Mitochondrion Schwann cell cytoplasm 5 m Smooth muscle cells Varicosities
The Sympathetic Division Summary of the Sympathetic Division Consists of parallel chains on either side of the spinal cord Preganglionic fibers are short and extend from the spinal cord to the sympathetic chain Postganglionic fibers are long and extend from the spinal cord to the body organs The sympathetic division shows considerable divergence All preganglionic neurons release ACh / most postganglionic neurons release norepinephrine
Figure 17.4 Anatomical Distribution of Sympathetic Postganglionic Fibers Eye PONS Salivary glands Superior Sympathetic nerves Cervical sympathetic ganglia Middle Inferior Gray rami to spinal nerves T 1 T 1 T 2 T 2 T 3 T 3 Greater splanchnic nerve Cardiac and pulmonary plexuses Heart Lung T 4 T 4 Celiac ganglion T 5 T 5 T 6 T 6 T 7 T 7 Superior mesenteric ganglion Liver and gallbladder T 8 T 8 Stomach T 9 T 9 T 10 T 10 T 11 T 11 Lesser splanchnic nerve Spleen Pancreas Postganglionic fibers to spinal nerves (innervating skin, blood vessels, sweat glands, arrector pili muscles, adipose tissue) T 12 T 12 L 1 L 1 L 2 L 2 L 3 L 3 L 4 L 4 Lumbar splanchnic nerves Inferior mesenteric ganglion Large intestine Small intestine Sympathetic chain ganglia L 5 L 5 S 1 S 1 S 2 S 2 S 3 S 3 S 4 S 4 S 5 S 5 Sacral splanchnic nerves Suprarenal medulla Kidney Spinal cord KEY Preganglionic neurons Ganglionic neurons Coccygeal ganglia (Co 1 ) fused together (ganglion impar) Uterus Ovary Penis Scrotum Urinary bladder
The Sympathetic Division ANIMATION The Distribution of Sympathetic Innervation
The Parasympathetic Division Parasympathetic Division Preganglionic neurons are in the brain stem and sacral segments Preganglionic neurons do not diverge as much as the sympathetic division Therefore, the parasympathetic division is more localized and specific as compared to the sympathetic division Postganglionic neurons are near (terminal) the target organ or within (intramural) the target organ
The Parasympathetic Division Organization and Anatomy of the Parasympathetic Division Preganglionic fibers leave the brain via: CN III (to the intrinsic eye muscles, pupil, and lens) CN VII (to the tear glands and salivary glands) CN IX (to the parotid salivary glands) CN X (to the visceral organs of the thoracic cavity and abdominal cavity) Preganglionic fibers leave the sacral region via: Pelvic nerves (to the visceral organs in the inferior portion of the abdominopelvic cavity
Figure 17.7 Organization of the Parasympathetic Division of the ANS Parasympathetic Division of ANS Preganglionic Neurons Ganglionic Neurons Target Organs N III Nuclei in Intrinsic eye muscles brain stem Ciliary ganglion (pupil and lens shape) N VII N IX Pterygopalatine and submandibular ganglia Nasal glands, tear glands, and salivary glands N X Otic ganglion Parotid salivary gland Intramural ganglia Visceral organs of neck, thoracic cavity, and most of abdominal cavity KEY Preganglionic fibers Nuclei in spinal cord segments S 2 S 4 Pelvic nerves Intramural ganglia Visceral organs in inferior portion of abdominopelvic cavity Postganglionic fibers
Figure 17.8 Autonomic Distribution of the Parasympathetic Output Pterygopalatine ganglion N III Lacrimal gland Eye PONS N VII Ciliary ganglion N IX Submandibular ganglion Salivary glands Otic ganglion N X (Vagus) Heart Lungs Autonomic plexuses (see Figure 17.9) Liver and gallbladder Stomach Spleen Pancreas Large intestine Pelvic nerves Small intestine Rectum Spinal cord S 2 S 3 Kidney S 4 KEY Preganglionic neurons Ganglionic neurons Uterus Ovary Penis Scrotum Urinary bladder
The Parasympathetic Division Functions of the Parasympathetic Division Pupil constriction Secretion of digestive enzymes from digestive glands Increased smooth muscle activity of the digestive system Stimulation and coordination of defecation Contraction of the urinary bladder Constriction of respiratory passages Reduced heart rate Sexual arousal
The Parasympathetic Division Parasympathetic Activation and Neurotransmitter Release All preganglionic and postganglionic fibers release ACh at their synapses and neuroeffector junctions Most stimulations are short lived due to the immediate breakdown of ACh by acetylcholinesterase
The Parasympathetic Division Plasmalemma Receptors and Responses Two types of ACh receptors are found on the postsynaptic plasmalemmae: Nicotinic receptors: respond to nicotine Found on surfaces of parasympathetic and sympathetic ganglionic neurons Muscarinic receptors: respond to muscarine Found on surfaces of parasympathetic cholinergic neuroeffector junctions
The Parasympathetic Division Summary of the Parasympathetic Division Involves CN III, CN VII, CN IX, and CN X Involves sacral segments S 2 to S 4 All parasympathetic neurons are cholinergic Release of ACh stimulates nicotinic receptors on ganglionic neurons Release of ACh on neuroeffector junctions stimulates muscarinic receptors
The Parasympathetic Division ANIMATION The Distribution of Parasympathetic Innervation
Relationships between the Sympathetic and Parasympathetic Divisions Sympathetic Widespread effect on visceral organs Parasympathetic Modifies the activity of structures innervated by specific cranial nerves and pelvic nerves Most vital organs are innervated by both the sympathetic and parasympathetic nerves The two often oppose (antagonistic) each other
Figure 17.10 A Comparison of the Sympathetic and Parasympathetic Divisions Sympathetic Parasympathetic CNS Preganglionic neuron PNS Sympathetic ganglion or Preganglionic fiber Ganglionic neurons KEY Neurotransmitters Acetylcholine Norepinephrine Epinephrine Circulatory system Postganglionic fiber Parasympathetic ganglion TARGET
Relationships between the Sympathetic and Parasympathetic Divisions Anatomy of Dual Innervation Head region The parasympathetic fibers accompany the sympathetic fibers to the target organ Thoracic and abdominopelvic regions The parasympathetic and sympathetic fibers mingle together forming plexuses Cardiac plexus Pulmonary plexus Esophageal plexus Celiac plexus Inferior mesenteric plexus Hypogastric plexus
Figure 17.9a The Peripheral Autonomic Plexuses Trachea Left vagus nerve Right vagus nerve Aortic arch Thoracic spinal nerves Autonomic Plexuses and Ganglia Cardiac plexus Pulmonary plexus Esophagus Splanchnic nerves Diaphragm Celiac trunk Thoracic sympathetic chain ganglia Esophageal plexus Celiac plexus and ganglion Superior mesenteric ganglion Superior mesenteric artery Inferior mesenteric artery Inferior mesenteric plexus and ganglion Hypogastric plexus Pelvic sympathetic chain This is a diagrammatic view of the distribution of ANS plexuses in the thoracic cavity (cardiac, esophageal, and pulmonary plexuses) and the abdominopelvic cavity (celiac, inferior mesenteric, and hypogastric plexuses).
Figure 17.9b The Peripheral Autonomic Plexuses Cranial nerve III Cranial nerve VII Cranial nerve IX Vagus nerve (N X) Autonomic Plexuses and Ganglia Trachea Cardiac plexus Esophagus Thoracic sympathetic chain ganglia Esophageal plexus Celiac plexus and ganglion Superior mesenteric ganglion Heart Diaphragm Stomach Inferior mesenteric plexus and ganglion Hypogastric plexus Pelvic sympathetic chain Colon Urinary bladder A sectional view of the autonomic plexuses
Visceral Reflexes Provide autonomic motor responses to: Modify or facilitate higher centers All are polysynaptic Reflexes can be: Long reflexes Short reflexes
Visceral Reflexes Long Reflexes Visceral sensory neurons go to the CNS via the dorsal roots There are interneurons within the CNS Information is interpreted in the spinal cord or brain ANS sends motor commands to the visceral organs
Visceral Reflexes Short Reflexes Sensory nerve impulses go to the ganglionic neurons Motor commands are distributed by the postganglionic fibers Impulses bypass the CNS
Figure 17.11 Visceral Reflexes Receptors in peripheral tissue Stimulus Afferent (sensory) fibers CENTRAL NERVOUS SYSTEM Long reflex Short reflex Response Peripheral effector Ganglionic neuron Autonomic ganglion (sympathetic or parasympathetic) Processing center in spinal cord (or brain) Preganglionic neuron